Mitsubishi QJ71C24N User Manual page 71

3 SPECIFICATIONS
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(2) RS-422/485 interface operation
1) RS-422-485 interface construction
The following illustration shows the construction of the Q series C24 RS-
422/485 interface driver (send)/receiver (receive).
2) RS-422/485 interface operation
When the "Output control input" in the illustration above is ON, the interface
enters the low impedance state (state in which data can be sent).
When the "Output control input" is OFF, the interface enters the high
impedance state (state in which data cannot be sent).
3) Timing to start sending and to complete the transmission processing for the Q
series C24
• Timing to start sending
During data transmission, the Q series C24 outputs the actual data after
sending a mark for 2 characters, or longer, after the high impedance set by
the operations described in 1) and 2) above is reset.
• Transmission processing completion timing
The following times are necessary as H/W gate OFF time from the time that
data transmission is completed until transmission processing is completed
(the state changes to the high impedance state). (The transmission rate set
in the Q Series C24 is the object.)
When the transmission rate
is 600 bps or higher
When the transmission rate
is 50 bps, 300 bps
(Output control input)
External device
Q series C24
(Output control input)
1 "Output control input" (also called send gate) of
the driver (send) section of the illustration at
the left determines whether or not data from
SDA/SDB is output to the outside.
: Data transfer time of less than 1 bit.
: several ms
Data
Outputs a mark for 2 characters, or longer
Data send time range
"Output control input"
ON time range
(Low impedance state)
Q series C24 is in the data
transmission and data
reception enable status
MELSEC-Q
Data
H/W gate OFF time
(See explanation above)
"Output control input"
OFF time range
(High impedance state)
Q series C24 is in the data
reception enable state.
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